Velocity-space signatures of shock-drift acceleration at quasi-perpendicular collisionless shocks

Gregory G. Howes; Alberto Felix; Collin R. Brown; Colby C. Haggerty; James Juno; Jason M. TenBarge; Lynn B. Wilson; Damiano Caprioli

doi:10.1063/5.0269528

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Velocity-space signatures of shock-drift acceleration at quasi-perpendicular collisionless shocks

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Velocity-space signatures of shock-drift acceleration at quasi-perpendicular collisionless shocks

Gregory G. Howes, Alberto Felix, Collin R. Brown, Colby C. Haggerty, James Juno, Jason M. TenBarge, Lynn B. Wilson and Damiano Caprioli

Physics of plasmas, Vol.32(6), 062904

06/2025

DOI: 10.1063/5.0269528

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Abstract

The shock-drift acceleration of ions at quasi-perpendicular shocks is a well-known kinetic mechanism for the acceleration of a small fraction of incoming ions to high energy. Here, we use a suite of sixteen hybrid simulations of quasi-perpendicular collisionless shocks over the range of Alfvén Mach number 4.3≤MA≤15.8 (corresponding to a range of fast magnetosonic Mach numbers 2.6≤Mf≤9.4) and shock-normal angle 45°≤θBn≤90° to identify the velocity-space signature of shock-drift acceleration using the field-particle correlation technique. We show that the features of the ion velocity distribution in the shock foot and ramp regions can be clearly interpreted by analysis of the single-particle trajectory of a reflected ion through the full 3D-3V phase space. The characteristic features of the velocity-space signature of shock-drift acceleration remain qualitatively robust over the full parameter range of our simulations, providing a potential means for its identification using single-point spacecraft measurements. At higher Alfvén Mach numbers MA≳8 ( Mf≳5), kinetic instabilities generate fluctuations of the electromagnetic fields within the shock transition region, leading to fluctuations in and smearing out of the resulting velocity-space signatures, but the signature remains generally robust and identifiable. The results on the shock-drift acceleration of ions presented here represent a novel means to determine more completely the partitioning of upstream bulk flow kinetic energy into plasma heating, particle acceleration, and electromagnetic fields in collisionless shocks.

Details

Title: Subtitle: Velocity-space signatures of shock-drift acceleration at quasi-perpendicular collisionless shocks
Creators: Gregory G. Howes - University of Iowa
Alberto Felix - Department of Physics and Astronomy, University of Iowa
Collin R. Brown - Plasma Physics Division, Naval Research Laboratory
Colby C. Haggerty - University of Hawaiʻi at Mānoa
James Juno - Princeton Plasma Physics Laboratory
Jason M. TenBarge - Princeton University
Lynn B. Wilson - Goddard Space Flight Center
Damiano Caprioli - University of Chicago
Resource Type: Journal article
Publication Details: Physics of plasmas, Vol.32(6), 062904
DOI: 10.1063/5.0269528
ISSN: 1070-664X
eISSN: 1089-7674
Publisher: AIP Publishing
Number of pages: 22
Grant note: 80NSSC20K1273 / Heliophysics Division (10.13039/100020016) 80NSSC24K0260 / Heliophysics Division (10.13039/100020016) 80NSSC18K1371 / Heliophysics Division (10.13039/100020016) 80NSSC18K0643 / Heliophysics Division (10.13039/100020016) 80NSSC23K0099 / Heliophysics Division (10.13039/100020016)
Language: English
Date published: 06/2025
Academic Unit: Physics and Astronomy
Record Identifier: 9984829885702771

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